WO2008053561A1

WO2008053561A1 - Electric field sensing element and display device making use of the same

Info

Publication number: WO2008053561A1
Application number: PCT/JP2006/322011
Authority: WO
Inventors: Akira Nakazawa
Original assignee: Shinoda Plasma Co., Ltd.
Priority date: 2006-11-02
Filing date: 2006-11-02
Publication date: 2008-05-08
Also published as: JP5297809B2; US20100067089A1; CN101535885A; EP2078980A4; JPWO2008053561A1; US8587855B2; EP2078980A1; KR20090086969A; US20110300667A1; CN101535885B; KR101354889B1; US8004737B2; EP2078980B1

Abstract

Electric field sensing element (1) comprising a metal oxide selected from the group consisting of tin dioxide, titanium dioxide and zinc oxide and an insulator covering the metal oxide, and further comprising optical functional layer (5) whose visible light transmittance value is changed by application of electric field and first and second electrode layers (7,9) having the optical functional layer (5) interposed therebetween.

Description

Specification

Electric field sensitive element and display device using the same

Technical field

The present invention relates to an element capable of controlling the value of visible light transmittance by applying an electric field, and a display device to which the element is applied.

Background art

[0002] Liquid crystals and electochromic substances are known as materials whose optical transmittance changes in response to an applied electric field. Liquid crystals are already widely used in displays. Electrochromic materials are materials that exhibit chromism (reversible color change) due to electrochemical redox reactions, and have various applications such as paper-like displays. It is a possible substance. A material that is sensitive to this type of electric field has the advantage that it is easier to control in terms of the configuration of the control means than a substance that is sensitive to light or heat.

[0003] Many of the electochromic materials are high molecular compounds synthesized chemically. Special Table 2000-502398 discloses that tin oxide doped with antimony or niobium exhibits electochromochromism. is there. The publication reports that a periodic color change that follows an electrical signal of 50 mHz has occurred (the response speed in this case is 20 seconds). Further, the above-mentioned publication describes that mixing a light color pigment such as titanium dioxide, silica, and alumina and doped tin oxide is effective in improving contrast.

Patent Document 1: JP 2000-502398

Disclosure of the invention

[0004] Compared to liquid crystal in terms of application to a display, the electochromic material does not require a polarizing plate or a knocklight, and thus is superior in terms of transparency in a translucent state and power consumption. However, since electoric chromism involves the movement of ions in the electrolyte, it is considered difficult to improve the response speed of the response in the electoric chromic material to the same or higher than that of liquid crystals. Changes in white and black in typical liquid crystals The response speed is 10-20ms.

[0005] The present invention provides a novel electric field sensitive element including a metal oxide that has a fast transition between states having different values of visible light transmittance. The electric field sensitive element of the present invention is composed of tin dioxide, titanium dioxide, and a metal oxide having a selected group force including an acid and zinc force, and an insulator covering the metal oxide. An optical functional layer whose visible light transmittance value changes by the application of, and first and second electrode layers sandwiching the optical functional layer.

[0006] A display device provided by the present invention covers a support having a light surface color, a first translucent electrode layer fixed to the support, and the first translucent electrode layer. An optical functional layer; and a second translucent electrode layer laminated on the optical functional layer. The optical functional layer is composed of a metal oxide selected from a group oxide such as tin dioxide, titanium dioxide, and acid zinc zinc, and an insulator covering the metal oxide. The value of visible light transmittance changes with the application of an electric field.

[0007] The manufacturing method provided by the present invention includes a step of coating the first electrode layer fixed to a support with a translucent layer comprising the metal oxide and an insulator covering the first oxide layer, Irradiating the translucent layer with ultraviolet rays, thereby transforming the translucent layer into the optical functional layer, and fixing the second electrode layer to the optical functional layer. .

Brief Description of Drawings

FIG. 1 is a cross-sectional view showing a configuration of an electric field sensitive element according to an example of the present invention.

FIG. 2 is a perspective view showing a configuration of a display device according to an example of the present invention.

FIG. 3 is a photograph of an oscilloscope waveform showing the response of the electric field sensitive element according to the first example of the present invention.

FIG. 4 is a photograph of an oscilloscope waveform showing the responsiveness of an electric field sensitive element according to a second example of the present invention.

FIG. 5 is an explanatory diagram of the operation principle of the electric field sensitive element according to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0009] The present inventor has applied an electric field when a semiconductor oxide having a band gap of 3.2 eV or more and translucent metal oxide is provided with an effective excitation energy in a state of being covered with an insulating coating. It has been found that the material can change the value of visible light transmittance. Tin dioxide ( SnO), titanium dioxide (TiO) and zinc oxide (ZnO) fall under the above metal oxides.

twenty two

The Insulation coating materials include thermoplastic resin such as polyethylene, polypropylene, polystyrene, polybutadiene, polychlorinated butyl, polymethyl methacrylate, polyamide, polycarbonate, polyimide, cellulose acetate, phenol resin, amino resin, unsaturated resin There are thermosetting resins such as polyester resin, aryl resin, alkyd resin, epoxy resin, polyurethane, silicone resin. Other examples include silicone (polysiloxane), paraffin, mineral oil, magnesium oxide (MgO), silicon dioxide (SiO 2), and alumina (Al 2 O 3).

2 2 3

[0010] By sandwiching the substance between electrode layers made of different materials as shown in Fig. 1, the electric field sensitive element 1 in which the value of visible light transmittance is reversibly changed is realized. In FIG. 1, the electric field sensitive element 1 includes an optical functional layer 5 whose visible light transmittance value changes by application of an electric field, a first electrode layer 7, and a second electrode layer 9. In the example, the first electrode layer 7 is a single layer, while the second electrode layer 9 is composed of a lower layer 9A, which is different from the material of the first electrode layer 7, and a material of the first electrode layer. It consists of the upper layer 9B which is the same as the material of 7. However, the lower layer 9A can be formed sufficiently thick and the upper layer 9B can be omitted.

In the layer structure of FIG. 1, the lower layer 9 A has a role of preventing unnecessary electron injection into the upper layer 9 B force optical function layer 5. By changing the material of the two conductors in contact with the optical functional layer 5, a reversible state change can be caused.

As an application example of the electric field sensitive element 1, there is a reflective display device 10 shown in FIG. The display device 10 includes a substrate 11 having a light surface color, strip-shaped first electrodes 17 arranged in parallel to be fixed to the substrate 11, an optical function layer 15, and an array in parallel to be fixed to the optical function layer 15. A strip-shaped second electrode 19 is provided. The first electrode 17 and the second electrode 19 intersect to form an electrode matrix. The electric field sensitive element 1 corresponds to each intersection of the electrode matrix. That is, the first electrode layer 17, the optical functional layer 15, and the second electrode 19 have partial forces corresponding to the first electrode layer 7, the optical functional layer 5, and the second electrode layer 9. In the figure, the position of one electric field sensing element 1 is indicated by a dashed-dotted line.

The display device 10 can perform matrix display by controlling the amount of external light reflected by the substrate 11 for each element. In the configuration in which the light to be controlled penetrates the electric field sensitive element 1 in the stacking direction as in this application example, the first and second electric field sensitive elements 1 As the electrode layers 7 and 9, it is necessary to provide a translucent conductive layer made of, for example, indium tin oxide (hereinafter referred to as ITO). When the first electrode layer 7 is ITO, a transparent semiconductor is preferable as the material for the lower layer of the second electrode layer 9.

The display device 10 and the electric field sensitive manufacturing method included in the display device 10 include the following steps 1 to 4.

[0015] In step 1, the first electrode 17 is arranged on the substrate 11 serving both as a support and a reflecting member.

[0016] In step 2, the first electrode 11 fixed to the substrate 11 is covered with a light-transmitting layer made of a metal oxide and an insulator covering the first electrode. Metal oxide is a compound selected from the group power of tin dioxide, titanium dioxide, and zinc oxide power.

[0017] In step 3, the light-transmitting layer is irradiated with ultraviolet rays, whereby the light-transmitting layer is transformed into an optical functional layer 15 exhibiting chromism. As for alteration, energy levels are considered to be formed in metal oxides by ultraviolet excitation as described later.

[0018] In step 4, the second electrode 19 is arranged on the optical functional layer 15.

Hereinafter, a specific example of the electric field sensitive element 1 will be shown.

Example 1

[0020] In Example 1, the optical functional layer 5 is composed of tin oxide (SnO), which is a metal oxide, and an insulator.

2 is formed using silicone oil as a material. The thickness of the optical functional layer 5 is 1 μm. The first electrode layer 7 is ITO having a thickness of 0.4 m. The lower layer 9A of the second electrode layer 9 is 0.1 μm thick nickel oxide (NiO), and the upper layer 9B is 0.4 μm thick ITO.

[0021] After the first electrode layer 7 was formed on a white plate glass having a thickness of 1 mm as a support by sputtering, the optical functional layer 5 was formed by the following procedure. A mixed solution of 0.75 g of tin cabronate, 1.28 g of xylene and 0. lg of silicone oil (TSF433 manufactured by Toshiba Silicone) was prepared. The above-mentioned mixed solution was applied by spin-on (1200 rpm, lOsec) to the white glass plate to which the first electrode layer 7 had been fixed, dried by exposure to lOmin in a 50 ° C. atmosphere, and then fired. The firing temperature is 320 ° C and the firing time is lOmin. Next, the fired layer was irradiated with ultraviolet rays using a low-pressure mercury lamp. Irradiation conditions are 200mWZcm ² and 60min.

[0022] After the optical functional layer 5 was formed, the lower layer 9A and the upper layer 9B were laminated by sputtering to complete the production of the electric field sensitive element 1. [0023] In order to confirm the optical function of the electric field sensitive element 1, a voltage pulse signal was applied to the electric field sensitive element 1. At that time, the first electrode layer 7 was connected to the potential output terminal of the pulse generator, and the second electrode layer 9 (strictly, the upper layer 9B) was connected to the ground terminal. As shown in the upper half of Fig. 3 (A), a positive pulse with an amplitude of +10 V and a pulse width of 20 ms and a negative pulse with an amplitude of 20 V and a pulse width of 20 ms were repeatedly applied with an interval of about 500 ms. . In parallel with this, the transmittance of the electric field sensitive element 1 with respect to visible light was measured using a measuring device using a light emitting diode (LED) as a light source.

[0024] As shown in the lower half of Fig. 3 (A), the transmittance value periodically changed in response to repeatedly applied pulses. A state change (referred to as “coloring”) occurs in response to the negative polarity pulse, and a state change in which the transmission value increases in response to the positive polarity pulse. Color "). During the pulse application interval, the state at the end of the previous change was maintained. The transmittance at the end of coloring was 80%, and the transmittance at the end of decoloring was 86%. FIG. 3A shows that Example 1 of the electric field sensitive element 1 exhibits chromism.

FIG. 3 (B) is a waveform diagram in which the scale of the time axis of FIG. 3 (A) is enlarged, and shows the response to the positive pulse! The decoloring response time was 5 ms.

[0026] FIG. 3 (C) is also a waveform diagram obtained by enlarging the time axis scale of FIG. 3 (A), showing the response to negative polarity pulses! The coloring response time was 8 ms.

Example 2

[0027] In Example 2, the optical functional layer 5 was insulated from titanium dioxide (TiO), which is a metal oxide.

It is formed from two materials, silicone oil. The thickness of the optical functional layer 5 is 1 μm. The materials, thicknesses, and formation methods of the first electrode layer 7 and the second electrode layer 9 are the same as in Example 1 above.

[0028] The optical functional layer 5 was formed by the following procedure. A mixed solution of 0.72 g of titanium caproate, 1.14 g of xylene, 0.14 g of butyl sequestration solvent and 0.25 g of silicone oil (TSF433 manufactured by Toshiba Silicone) was prepared. The above-mentioned mixed solution was applied to the white plate glass to which the first electrode layer 7 was fixed by spinons (600 rpm, lOsec), dried by exposure to lOmin in a 50 ° C. atmosphere, and then fired. The firing temperature is 320 ° C and the firing time is lOmin. Next fired layer Were irradiated with ultraviolet rays using a low-pressure mercury lamp. The irradiation conditions are 200 m W / cm ² and 60 min as in Example 1.

[0029] The optical function of the electric field sensitive element 1 was confirmed by the same method as in Example 1. That is, as shown in the upper half of Fig. 4 (A), a positive pulse with an amplitude of +10 V and a pulse width of 20 ms and a negative pulse with an amplitude of 20 V and a pulse width of 20 ms are provided with an interval of about 500 ms. Applied repeatedly. In parallel with this, the transmittance of the electric field sensitive element 1 with respect to visible light was measured using a measuring device using an LED as a light source.

[0030] As shown in the lower half of Fig. 4 (A), the transmittance value periodically changed in response to the repeatedly applied pulses. A state change (coloring) in which the transmittance value decreased in response to the negative polarity pulse occurred, and a state change (decoloration) in which the transmittance value increased in response to the positive polarity pulse occurred. During the pulse application interval, the state at the end of the previous change was maintained. The transmittance at the end of coloring was 79%, and the transmittance at the end of decoloring was 92%. FIG. 4A shows that Example 2 of the electric field sensitive element 1 exhibits chromism.

[0031] FIG. 4 (B) is a waveform diagram obtained by enlarging the time axis scale of FIG. 4 (A), and shows the responsiveness to the positive pulse! The decoloring response time was 17 ms.

FIG. 4 (C) is also a waveform diagram obtained by enlarging the time axis scale of FIG. 4 (A), and shows the response to negative polarity pulses. The color response time was 18 ms.

Example 3

[0033] A mixed liquid of 2 g of tin caproate, 3 g of xylene and 0.5 g of silicone oil (TSF433 manufactured by Toshiba Silicone Co., Ltd.) was prepared, and the mixed liquid was applied, dried, fired, and irradiated with ultraviolet rays in the same manner as in Example 1. To form an optical functional layer 5.

The second electrode layer 9 was grounded, and a negative polarity pulse having an amplitude of 20 V and a pulse width of 10 ms was applied to the first electrode layer 7. In response to the pulse application, the transmittance value of the electric field sensitive element 1 changed from 85% to 56%. Thereafter, the transmittance value was maintained at 56% during the period when the applied voltage was zero.

Example 4

A mixed solution similar to that in Example 3 was prepared, and dried more rapidly than Example 3 after coating.

Other than that was the same as Example 3. [0036] By rapidly drying the applied mixed liquid, voids due to solvent evaporation remain, and the layer after baking becomes a particle aggregate. The porous optical functional layer 5 improves contrast. In response to the same pulse application as in Example 3, the transmittance value of electric field sensitive element 1 changed from 85% to 24%.

[0037] Regarding the chromism confirmed in the above embodiments, the operation principle shown in Fig. 5 can be considered. The power to take tin dioxide as an example The following explanations also apply to titanium dioxide and zinc oxide.

[0038] As shown in Fig. 5 (A), when one of the electrodes, ITO, which is a metal oxide on ITO, is irradiated with ultraviolet light, electrons in the valence band of tin dioxide are conducted. Excited by the band. In the vicinity of the interface with ITO, this electron passes through the insulator with a certain probability and is temporarily trapped in ITO, and the interatomic distance at the site where the electron in the valence band has escaped changes. The trapped electrons return to the valence band of tin dioxide again. The level at this time moves into the band gap as shown in Fig. 5 (B). Such an event occurs repeatedly, and many levels are formed in the band gap as shown in Fig. 5 (C) while the ultraviolet rays are irradiated. However, electrons that should be trapped in these levels are excited by ultraviolet rays and move to ITO. The level in the band gap in the absence of electrons thus generated remains even after the ultraviolet irradiation is finished. The energy (wavelength) of light absorbed by the metal oxide depends on the level in the band gap. In the case of tin dioxide, the transmittance value is large when the number of electrons in the band gap is small (transparent state).

[0039] The role of the insulator is to create a barrier between ITO and tin dioxide and allow the excited electrons to pass. Tin dioxide undergoes a structural change when it is exposed to ultraviolet radiation with an insulator between ITO and tin dioxide.

[0040] When an electric field is applied to tin dioxide in a transparent state having a level in the band gap as shown in Fig. 5 (D), the ITO electrons move to the tin dioxide across the barrier due to the insulator. When the transferred electrons are trapped in the band gap level of tin dioxide, the transmittance value of tin dioxide decreases. In other words, the transparent state force also changes to a dark color state. Even when the electric field is removed, the dark state is maintained by the charge on the barrier.

[0041] As shown in Fig. 5 (E), when an electric field having the opposite polarity to the previous one is captured, it is trapped in the band gap. The emitted electrons are external light with an amount of light equivalent to room lighting such as phosphors, and become free electrons in the conduction band with a certain probability. These free electrons move to ITO. As a result, the state in the bandgap finally has no electrons. This restores the dark state force to a transparent state.

[0042] According to the above embodiment, since the transmittance value in a state where decoloring has occurred is large, it is possible to realize a reflective display device with high contrast and a bright background. Since the main component of the electric field sensitive element 1 is a solid, damage due to mechanical impact is less likely to occur compared to a configuration in which all liquids or liquids are contained. Since the structure is simple, it is advantageous for low cost.

[0043] In the manufacturing method of the above embodiment, the insulating material is limited to a heat-resistant material that can be fired. However, when a manufacturing method in which silicone oil is washed and removed after baking and a new resin is filled, A resin such as acrylic, polycarbonate, and epoxy can be used.

[0044] The electric field sensitive element of the present invention, which is embodied by the above embodiment or its modification, has the following applications.

[0045] Since the amount of change in transmittance is proportional to the applied voltage, multi-tone expression can be achieved by multi-value control of the applied voltage. Using a knocklight and a filter, full-color display similar to liquid crystal is possible.

[0046] The optical functional layer 5 whose structure is partially changed by ultraviolet irradiation of an arbitrary pattern can be formed, and an arbitrary shape can be displayed by a combination of the irradiation pattern and the electrode layer pattern.

As a modification of the display device 10, a substrate in which a reflective film is fixed to a rigid or flexible base material by lamination or painting can be used as a support for the electric field sensitive element 1.

[0048] The configurations, materials, manufacturing methods and materials, etc. of the electric field sensitive element 1 and the display device 10 are not limited to the examples, and can be appropriately changed within the scope of the gist of the present invention. Industrial applicability

[0049] The present invention is useful in a power-saving display that consumes power only when the display content is substantially updated. It can be used for various optical function devices including other displays and optical shirts.

Claims

The scope of the claims

[1] Consists of a metal oxide selected from the group consisting of tin dioxide, titanium dioxide, and zinc oxide, and an insulator covering the metal oxide, and transmits visible light when an electric field is applied. An optical functional layer in which the value of the rate changes;

First and second electrode layers sandwiching the optical functional layer

An electric field sensitive element characterized by that.

[2] The electric field sensitive element according to claim 1, which exhibits chromism.

[3] The material of the first electrode layer is different from the material of the second electrode layer

The electric field sensitive element according to claim 2.

[4] The first electrode layer is made of a transparent conductive material different from the metal oxide,

4. The electric field sensitive element according to claim 3, wherein at least a portion of the second electrode layer in contact with the optical functional layer is a P-type semiconductor force.

[5] The first electrode layer is made of indium tin oxide,

The metal oxide is tin dioxide;

5. The electric field sensitive element according to claim 4, wherein a portion of the second electrode layer that is in contact with the optical functional layer has an acid-nickel force.

[6] Response time to electric field application is 10 ms or less

The electric field sensitive element according to claim 5.

[7] The first electrode layer is made of indium tin oxide,

The metal oxide is titanium dioxide;

[8] Response time to electric field application is 20 ms or less

The electric field sensitive element according to claim 7.

[9] a support having a light surface color;

A first translucent electrode layer fixed to the support;

An optical functional layer covering the first translucent electrode layer;

A second translucent electrode layer laminated on the optical functional layer, The optical functional layer is composed of a metal oxide selected from the group consisting of tin dioxide, titanium dioxide, and acid-zinc carbonate, and an insulator covering the metal oxide. Visible light is applied by applying an electric field. Transmissivity value changes

A display device characterized by that.

A method of manufacturing an electric field sensitive element according to claim 1,

Coating the first electrode layer fixed to the support with a light-transmitting layer comprising the metal oxide and an insulator covering the metal oxide;

Irradiating the translucent layer with ultraviolet light, thereby transforming the translucent layer into the optical functional layer; and

A step of fixing the second electrode layer to the optical functional layer.

A method for manufacturing an electric field sensitive element.